Key facts & rules

• Ionic bonding: metal loses electrons (→ cation) + non-metal gains electrons (→ anion) → electrostatic attraction.
• Ionic compounds: high melting point, conduct electricity when dissolved or molten, form crystals.
• Covalent bonding: non-metals share pairs of electrons.
• Simple molecular: low melting/boiling point, do NOT conduct electricity (e.g. H₂O, CO₂, CH₄).
• Giant covalent: very high melting point, hard, do NOT conduct electricity (except graphite). E.g. diamond, SiO₂.
• Metallic bonding: lattice of positive ions surrounded by a 'sea' of delocalised electrons.
• Metals: conduct electricity/heat, malleable, ductile — because of delocalised electrons.
• Hydrogen bonds: strong intermolecular forces in water and between N−H/O−H groups.
• Van der Waals forces: weak, temporary dipole attractions — exist between ALL molecules.